Wednesday, 29 January 2014

Cylindrical Structures in Potsdam Group Sandstone in Eastern Ontario

Cylindrical sandstone structures that cut across the bedding in Potsdam Group sandstones in Eastern Ontario at locations north of Kingston have been written about by geologists for over one hundred years.   Two of the earliest reports were written by T.C. Weston of the Geological Survey of Canada and report the results of his visit in 1888 to the locality, a quarry about twelve miles north of Kingston on the east bank of Cataraqui River four miles above the locks of the Rideau Canal at Kingston Mills.   The two references are:

Weston, T.C. (1895), Notes on Concretionary Structure in Various Rock Formations in Canada,   Transactions of the Nova Scotian Institute of Science, Session of 1891-92, Volume VIII, Being Volume I of the Second Series, pages 137 - 142 (a paper read November 9th, 1891 before the Nova Scotian Institute)

Weston, T.C. (1899), Reminiscences  Among The Rocks, Warwick Brothers & Rutter, Toronto, Ontario, at pages 247 -248 (an autobiography recording Weston’s employment with the Geological Survey of Canada).


This is how Weston (1899) described his visit:

    “During this year, 1888, much discussion prevailed concerning the discovery of supposed fossil trees, many examples of which are seen in the Cambrian (Potsdam) formation on the banks of the Rideau Canal, Kingston, Ont.   The attention of the director of the Canadian Geological Survey [Dr. Selwyn] was drawn to these singular forms; he visited the locality and caused a section of one measuring four feet in diameter to  be sent to the museum in Ottawa. 

        On the director's return I was requested to visit the locality, and on the 16th of October, accompanied by Mr. Topley, the Government photographer, we started, and on arriving at Kingston found several people much interested in the discovery of these so called “fossil trees." In a shop window we saw a section of one labelled “Section of a stone tree." Hiring a team we drove through the historical city of Kingston.  Our twelve mile drive to the celebrated quarry where these so-called fossil trees occur was a pleasant one.

        We found quite a number of these cylindrical forms, some examples would weigh many tons;  some of the weathered sections show irregular concentric rings which resemble somewhat the lines of growth in exogen plants. No fossil trees have yet been discovered in the Cambrian formation to which these deposits belong, and the conclusion arrived at was that these tree-like bodies are of concretionary structure, formed probably in geyser cavities. The "potato-stones" found in these sandstones are nodules, formed of the same material which composes these rocks.  The photographs taken at this interesting locality are the property of the Geological Survey and can be seen at that institution.”

Two drawings of the cylindrical structures were provided in Weston (1895).  The first is provided below.



Below is a photograph of the same outcrop  provided in a guidebook published in 1913 that was prepared by M. B. Baker [Baker, M.B. (1913), Excursion A9 - Mineral Deposits Near Kingston, Excursions in the Eastern Townships of Quebec and the Eastern Part of Ontario, Guide Book No. 2,  12th International Geological Conference in Canada 1913]





When Weston visited the quarry it was known as the Gildersleeve quarry.  In Baker’s guide it is called Blake’s quarry.  It is now known as the Hughes quarry.   Interestingly, that outcrop is still visible at the ‘Park of Pillars’ at the Hughes quarry,  Lots 8 and 9, Concession V, Pittsburgh Township.   See both: 

(1) the photographs that are Figure 40  in B.V. Sanford and R.W.C. Arnott (2010), Stratigraphic and structural framework of the Potsdam Group in eastern Ontario, western Quebec and northern New York State, GSC Bulletin 597

(2) the photograph of Site E15 at Let’s Rock,
http://planetrocks.ca/e15-geologic-columns-tracking-weird-structures-in-the-potsdam-sandstone/

The second drawing of the cylindrical structures from  Weston (1895) is a  weathered cross-section showing well defined concentric rings. 


William James Topley

William James Topley (1845 - 1930), the photographer that accompanied T.C. Weston to look at the “fossil trees”, was one of the most important photographers in Canada in the late 1800's.    Over 150,000 of Topley’s negatives and photographs are in the collection of Archives Canada.   Unfortunately, it is not presently possible to search the whole of the collection online, and I could not locate his original photographs of the cylindrical structures in the archives.

I may have found one of Topley’s photographs in the following publication of the New York State Museum:  Cushing, H. P., Fairchild, H.L, Ruedemann, R. And Smyth, C.H. Jr. (1910), Geology of the Thousand Islands Region, New York State Museum Bulletin 145.  Plate 13 of that publication contains two photographs from the Gildersleeve quarry.  The right hand photograph was taken by Dr. H. M. Ami of the Geological Survey of Canada.  The left hand photo is credited simply to the Geological Survey of Canada, and may be one of Topley’s.   The photos of the cylindrical structures from Ontario  were included “because, while corresponding precisely to the New York State examples, it furnishes a much better illustration than any there seen.” 






Theories for The Origin of the Cylindrical Structures

There have been many theories proposed to explain the origin of the cylindrical structures.   The weight of authority currently favours dewatering processes, but numerous other theories have been advanced over the years.   Sixty-one years ago R. V. Dietrich, in a report on similar structures in the Potsdam Sandstone of New York State,  summarized the prevailing views as follows:

    “Similar structures in the Potsdam sandstone of this region have been previously described and interpreted to represent concretions, concretionary structures formed in geyser cavities, sediments deposited in whirlpools in potholes, and typical flat-lying Potsdam sandstone in which the original pigmentation was modified by the rising of springs through the unconsolidated Potsdam sand, the affected areas subsequently undergoing concretionary cementation.
    ...
    [Sir William Dawson] (1889) suggested that the structures in the Potsdam sandstone in the Ontario-New York area represent concretions that formed around organic cores.   Weston (1899) suggested that the structures are concretions formed in geyser cavities.  Ells (1905) referred to the structures as cylindrical concretions, but offered no explanation for their shape or origin. W.G. Miller (1906) and Cushing (1910) concurred with the connotation, concretion, and also refrained from giving a generic discussion.  Baker (1916) suggested that they represent sediments deposited by whirlpools or other edying water in potholes.  Hawley and Hart (1934) ... concluded that they “...are considered to have formed during, or after, deposition of sand, but before final cementation.  The concentric, cylindrical color banding is believed to be concretionary in nature, localized by the presence of vertical cylinders of uncemented and not excessively disturbed sand.  The formation of these is attributed to the actions of currents of water, rising vertically through the strata from, possibly, a buried fault line or other controlling structure...”.”

[Dietrich, R.V. (1953), Conical and Cylindrical structures in the Potsdam Sandstone, Redwood, New York, New York State Museum Circular 34, at pages 5 & 9]   

Interestingly, Dietrich favoured a “slumping” origin and concluded that “Field relationships suggest that the structures at the Redwood locality were formed by the movement of unconsolidated and/or partly consolidated sand into cavities developed in underlying sand by falling of that sand into cavities in the underlying marble of the Precambrian Grenville Series.”

A more recent summary of the differing views for their origin can be found in B.V. Sanford and R.W.C. Arnott (2010), Stratigraphic and structural framework of the Potsdam Group in eastern Ontario, western Quebec and northern New York State, GSC Bulletin 597, at page 41, where they comment:


    “The origin of these structures has been the subject of speculation for a great many years, and the controversy likely will not be settled until such time as one of the columns can be dismantled at its base to determine whether it originated from the bottom or top. ... The origin of these structures... has been attributed to fossil tree trunks, potholes excavated and later infilled with sand, concretions, collapse or local slumping of sand into cavities in underlying Precambrian marble, and dewatering processes.  As proposed by Sanford (2007), a logical explanation for the origin of the columns is that of potholes later infilled with sand, as a fair amount of evidence suggests that they were drilled from the top down by rotating quartzite cobbles caught up in vortices on the floor of high energy systems, much like the motion of a diamond bit drilling into bedrock.”

That suggestion notwithstanding, the majority of recent commentators favour dewatering processes.


Locations in Ontario Where the Cylindrical Structures Have Been Found


Cylindrical sandstone structures that cut across the bedding in Potsdam Group sandstones in Eastern Ontario have been found at three quarries to the north of Kingston and Gananoque, namely:

A) the Hughes quarry, Lots 8 and 9, Concession V, Pittsburgh Township, Frontenac County;

B) the Sloan quarry, Lot 11, Concession VI, Storrington Township, Frontenac County;

C) the Ellisville quarry at Ellisville, Ontario, Lots 19 and 20, Concession VII,  Rear of Leeds and Lansdowne Township, United Counties of Leeds and Grenville.

Similar structures have been reported in two cliffs in lots 21 and 22 , Concession X of Storrington Township, “on the sandstone tongue, along which the road runs, at the north side of Dog Lake” (Baker, M.B. (1916), The Geology of Kingston and Vicinity, Ontario Bureau of Mines, Vol. XXV., Part III, No. 4, page 19).  


Cylindrical sandstone specimens were also collected from Potsdam sandstones near Almonte  (See: Dawson, W. J.  (1889),  Remarks of the President on Certain Ancient Concretions, Canadian Record of Science, Volume 3, pages 293-294 (read November 26, 1888 before The Natural History Society, Montreal);  Dawson, W. J.  (1890) On Burrows and Tracks of Invertebrate Animals in Palaeozoic Rocks , and Other Markings, London Quart. Journal Geol. Soc. 46, pp. 595-617 at pages 609-610 (Read May 14, 1890).

Dawson (1890) also reports that “Many years ago specimens were obtained from the Potsdam Sandstone of Ontario, by the late Sir William Logan, which presented the aspect of large cylindrical trunks, a foot or more in diameter. ... showing obscure concentric lines on the ends.  No opinion was, I believe hazarded at that time respecting their origin...”   I have not been able to determine where in Ontario Logan obtained those specimens.


I’ve been told by two geologists that they are also present in the sandstone around Charleston Lake. 

I have not yet found a similar structure in the Potsdam Group sandstones close to Perth, but I'll keep looking.

Christopher Brett
Perth, Ontario


[Added: September 30, 2015:

For cylindrical structures at
Charleston Lake Provincial Park see:   

Donaldson, J.A. and Chiarenzelli, J. R.,2004,
Pre-Cambrian Basement and Cambrian-Ordovician Strata, as Displayed in Three Provincial Parks in Canada, Trip A-1, New York Geological Association, 76th Annual Meeting Field Trip Guidebook,  pages 63-78.  Stop 6 - Charleston Lake Provincial Park, Giant Cylinder in Nepean Formation, at page 74.     Figure 11 at page 76 has the caption “The cylindrical structure along Sandstone Island Trail, Charleston Lake Provincial Park. 

Forsyth, D.A. and Forsyth, M.E., 2011,
Pillars in the Park, 

GAC/AGC - MAC/AMC - SEG - SGA  Joint Annual Meeting, Ottawa 2011, Abstracts Volume 34, at page 66
They report on “sandstone cylinders or pillars” in Charleston Lake Provincial, noting that “At least 8 cylinder sites are hosted by the sandstone plateau in the Provincial Park. These “water escape” features in the form of cylinders or pillars may be the lithified remains  of water table spring conduits that developed in response to water flow through very clean and well sorted sand overlying undulating Precambrian surface topography. Various cylinder forms resemble active, lithified and unconsolidated structures reported  from the USA and the Himalayas as well as some reported from more recent glacial sand deposits in Quebec.” ]




Friday, 29 November 2013

Additional Geological Field Trip Guides for Eastern Ontario That Are Available Online

My last blog posting reported on a new geological field trip guide that is a 40 kilometer bike tour that starts in Perth.   There are a number of additional geological field trip guides for Eastern Ontario that are available online, including the ones mentioned below.   The first two guides were posted to the internet this year, as was a guide to the Kingston area.

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MADAWASKA TO MACNAMARA TRAIL AND MACNAMARA TRAIL GEOTOURS, ARNPRIOR
by Dave and Mary Forsyth, 2013. Macnamara Field Naturalists Club. 

http://www.mfnc.ca/images/images_frontend/pdf/arnpriorgeotour.pdf

This provides two geological field trip guides:   the first is along the Madawaska to the  Macnamara Trail; the second is along the Macnamara Trail.   Both trails are in Arnprior, Ontario and fall within the Nopiming Game Sanctuary,  a Crown Game Preserve solely on private land.

The Macnamara Nature Trail is an interpretive trail that is maintained by the Macnamara Field Naturalists Club in Arnprior.   The trail is approximately four kilometres long with an optional one kilometre branch. The main trail is marked with blue-and-white hiking symbols.     A guide to the nature and features at the 19 numbered stops along the trail can be downloaded from:

http://www.mfnc.ca/images/images_frontend/pdf/macnamaratrailguide.pdf

Where to park your car is set out at  http://www.mfnc.ca/macnamaratrail.html

Dave and Mary Forsyth’s geological guide supplements the nature guide.

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A GEOLOGY PRIMER FOR THE MORRIS ISLAND CONSERVATION AREA 
by Dave and Mary Forsyth, 2013.  Macnamara Field Naturalists Club. 

http://www.mfnc.ca/images/images_frontend/pdf/morrisislandconversationarea_geology.pdf

This guide has 11 stops along trails through the Morris Island Conservation Area

The Morris Island Conservation Area is located along the Ottawa River just west of the community of Fitzroy Harbour.  This 47 hectare site consists of forested woodlands and wetlands.  The Mississippi Valley Conservation manages this site for day-use recreational activities such as hiking, picnicking, canoeing, fishing and natural interpretation. Morris Island Conservation Area is open to the public year round and is jointly owned by Ontario Power Generation and the City of Ottawa.  See:

http://ontarioconservationareas.ca/component/mtree/conservation-authorities-of-ontario/mississippi-valley/morris-island-conservation-area

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OTTAWA-GATINEAU GEOLOGICAL FIELD TRIPS
From Professor Allan Donaldson's course in the Learning in Retirement Seminars at Carleton University.

http://http-server.carleton.ca/~jadonald/fieldtrips.html

This guide contains six trips, including to the outcrop of Stromatolites on the Quebec side of the Champlain Bridge (which are best viewed when the Ottawa River is low).

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GEOLOGY OF THE OTTAWA AREA
Ottawa-Gatineau Geoheritage Project Field Trip
Compiled by Quentin Gall
November, 2010

http://www.ottawagatineaugeoheritage.ca/downloads/Geology%20Of%20The%20Ottawa%20Area.pdf

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FIELD TRIPPING: GEOLOGY OF THE KINGSTON AREA
By H.H. Helmstaedt,  W.A. Gorman & S.L. McBride, Department of Geological Sciences, Queen’s University, Kingston, Ontario, Canada, K7L 3N6,
1987

www.whaton.uwaterloo.ca/waton/s906.html

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FIELD TRIP GUIDE: GEOLOGY OF THE KINGSTON AREA
80th Meeting of Eastern Section of the Seismological Society of America at Queen’s University, Kingston, Ontario, Canada, October 5, 2008

Field Trip Leader: Laurent Godin
Field Trip Guide prepared by H. Helmstaedt and L. Godin
Department of Geological Sciences and Geological Engineering
Queen’s University, Kingston, Ontario, Canada K7L 3N6

http://geol.queensu.ca/ESSSA2008/field_trip_manual.pdf

Five stops, including the Holleford Crater.

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GEOLOGY OF THE KINGSTON AREA: 1.1 BILLION YEARS OF EARTH HISTORY
GeoEngineering Centre Field Trip 2013
Miller Museum of Geology
Miller Hall, Queen’s University

http://www.geoeng.ca/GeoEngCentre_fieldtrip2013_fullDescription%5B1%5D.pdf
   
Six stops, including the Abbey Dawn roadcut (a good example of an unconformity).

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GEOTOUR  OF  FRONTENAC  ARCH  BIOSPHERE  RESERVE
Sunday, October 5, 2008
Geological Notes Prepared by Allan Donaldson & Chris Findlay,
Friends of Canadian Geoheritage

http://www.explorethearch.ca/sites/explorethearch.ca/files/GeoTour_Guidebook_2008_reduced_0.pdf

Ten Stops, starting at the Lyn Valley Conservation Part, and returning to Brockville.  Aimed at field naturalists.

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FALL GEOLOGY/ECOLOGY BOAT TOUR - ST LAWRENCE RIVER  1000  ISLANDS
October 17, 2010
Geology/Ecology Tour Guides: Al Donaldson, Dave Forsyth, Chris Findlay and Bud Andress,

http://www.frontenacarchbiosphere.ca/explore/fab-education/geology/st-lawrence-river-thousand-islands-geology-boat-tour

This tour starts at Mallorytown Landing and proceeds along the St. Lawrence River to Gananoque.  It visits 8 sites that illustrate the major geological components of the region. At each stop the descriptions in the guide discuss the rock types and  geological features.   Looks to be a great tour for a summer’s day, if you have a boat.

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DEGLACIATION OF THE CHAMPLAIN SEA BASIN, EASTERN ONTARIO

By Hazen A. J. Russell and Don I. Cummings (field-trip leaders)
Geological Survey of Canada
With contributions from  Jan Aylsworth, Greg Brooks, Jean-Pierre Guilbault, Marc Hinton, AndrĂ© Pugin, Susan Pullan, and  David Sharpe

http://www.geology.um.maine.edu/friends/pdf/FOP2009Guide.pdf

Abstract:  The Champlain Sea was an inland arm of the Atlantic Ocean that invaded the St. Lawrence Lowland  following retreat of the Laurentide Ice Sheet. This field trip reviews a number of aspects of the deglacial landforms and deposits of the area, discusses the Champlain Sea deposits and reviews the societal  implications of the deposits from a geotechnical and hydrogeological perspective. Day one of the two day trip is spent on the Vars - Winchester esker which provides an opportunity to discuss esker and Champlain Sea deposits and to highlight the geotechnical and hydrogeological issues associated with these deposits. Day  two of the trip visits the Cantley quarry and discusses the evidence for and against subglacial meltwater erosion for the sculpted forms at the site.

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TECTONIC HISTORY OF THE GRENVILLE PROVINCE, ONTARIO
Field Trip Guidebook A5, Precambrian ‘95
Geological Survey of Canada, Open File 3142
By A. Davidson, 1995

http://ftp2.cits.rncan.gc.ca/pub/geott/ess_pubs/205/205286/of_3142.pdf

This six day field trip is for geologists with a serious interest in the Grenville Province of the Canadian Shield,  rather than field naturalists, but does provide the location of some outcrops that will be of interest to field naturalists.

Day 5: Bancroft to Sharbot Lake.  Stop 5-10 is a photogenic outcrop of pillowed basalts at the junction of County Roads  41 and 506  south of Bon Echo Provincial Park  (see:
http://naturallyrichfrontenacs.com/bedrock.html )
Day 6: Sharbot Lake to Gananoque

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Christopher Brett
Perth, Ontario

Wednesday, 6 November 2013

Murphys Point Bike Loop: A Geological Interpretation, by Bradley S. Wilson


This fall saw the release of a new geological field trip guide that covers part of Lanark County. Entitled  Murphys Point Bike Loop: A Geological Interpretation, the twenty-four page brochure was written by Brad Wilson a consulting geologist based in Kingston, Ontario.  It was prepared with the financial support of Ontario’s  Highlands Tourism Organization Recreational Geology Project.

Free paper copies of the brochure can be obtained from the tourism office in the Perth Museum,  Matheson House, at 11 Gore Street East in Perth, and from the  tourism office in the Perth & District Chamber of Commerce office in the Old Fire Hall with Hose Tower, at 34 Herriott Street in Perth.   A pdf copy of the brochure can be downloaded from:

http://sgraycomm.files.wordpress.com/2013/08/murphys-point-bike-loop-aug5-13-final-download-small.pdf

The geological guide covers a 40 kilometer bike loop from Perth to Murphys Point Provincial Park and back along flat country roads.  The author estimates this to be a three hour bike ride.  The route starts in Perth, goes south-east along Rideau Ferry Road (County Road 1), south along Elm Grove Road (County Road 21) which becomes Lally Road, north along Narrows Lock Road (County Road 14 ) and north-east along Scotch Line (County Road 10), returning to Perth.   Below is the map from the brochure.

























The guide is clearly written and will likely be enjoyed by both those with a geological background and field naturalists.  It contains numerous figures and colour photographs of outcrops, and the above map showing the location of all eighteen stops on the tour.   The first five pages of the brochure provide an introduction to the geology of Lanark County.   Highlights of the tour include outcrops where glacial striae are visible, an unconformity between rocks of the Precambrian Shield and overlying Paleozoic rocks, the type locality for Perthite, and  a visit to the Silver Queen Mica Mine. 

The best part of the brochure, besides the clear writing style of the author, is that it doesn’t try to cover all of the outcrops along the tour.   It leaves many outcrops to be discovered and explored.

While written for a bike tour, it also works as a field trip guide for those that would rather drive.  However, two points should be kept in mind if you drive.   First, there are some deep ditches beside some of shoulders of the road, and care should be taken when parking.   Second, the tour passes through Murphys Point Provincial Park, and one has to pay to park in the parking lots in the park (for example, the parking lot closest to the Silver Queen Mine, which is part of the park).

This is the second recent geological brochure for Lanark County that has been prepared with the support of Ontario’s  Highlands Tourism Organization Recreational Geology Project.   The first, released a little a year ago, is entitled Introduction to the Geodiversity of Perth: A Self-Guided Tour of Rocks on Display at the Crystal Palace, Tay Basin, Perth, Ontario and was written by Dr. Allan Donaldson, a retired professor of Earth Sciences, Carleton University.   This fourteen page brochure is a walking tour.    This is also a clearly written brochure with colour photographs.  Paper copies of this brochure can also be obtained from the tourism office in the Matheson House Museum in Perth, and from the tourism office in the Chamber of Commerce in Perth.   It can also be downloaded in pdf format from:

http://www.perthtourism.ca/uploads/1/6/1/3/16138712/perth_geohistory_booklet.pdf

If you stop at the Matheson House Museum in Perth to pick up copies of either brochure, be sure to look at the rocks, minerals and fossils on display on the top floor of the museum. 

Christopher Brett
Perth, Ontario

Addendum (October 6, 2016)

Introduction to the Geodiversity of Perth: A Self-Guided Tour of Rocks on Display at the Crystal Palace, Tay Basin, Perth, Ontario, by Dr. J Allan Donaldson

This brochure can now be downloaded in pdf format from the Stephanie Gray’s web site at:

https://sgraycomm.files.wordpress.com/2013/08/perth-geohistory-booklet-sept20-small.pdf

Friday, 13 September 2013

A Selection of Fossils from the March Formation in Lanark County, Ontario

A year ago I collected a number of specimens of fossils, and photographs of fossils, from a quarry in Lanark County about a five minute drive north of Perth.  The quarry is in lot 10, concession  IV of Drummond Township.  The quarry falls in an area that has been mapped as the March Formation.   It is a section of flat lying beds of sedimentary rock (primarily sandstone)  that in an earlier posting I described as the Drummond Sequence as it falls in an area that was surveyed as Drummond Township.   The Drummond Sequence is bounded by faults that separate it on the west from Nepean Formation (Potsdam Group) sandstones, on the southeast from March Formation, on the northeast from Nepean Formation sandstones, on the north from Precambrian Shield and on the northwest from Precambrian Shield.  It has an irregular shape and covers over 100 square kilometers.  It can be viewed on Ontario Geological Survey Maps P2724 and P 2725 that can be downloaded from:

P2724 - Paleozoic geology, Perth area, southern Ontario
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/P2724/P2724.pdf

P2725 - Paleozoic geology, Carleton Place area, southern Ontario
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/P2725/P2725.pdf

 (The March Formation is unit “3" on the maps, while the Nepean Formation is unit  “2".)

The March Formation is generally considered to be Lower Ordovician in age and is equivalent to the Theresa Formation in Quebec and New York State.  As originally envisaged by Sir William Logan of the Geological Survey of Canada it was the passage or transition beds between the underlying Potsdam Sandstone and the overlying Calciferous formation.   In 1937, 1938 & 1946  Alice E. Wilson of the Geological Survey of Canada renamed the Potsdam Sandstone as the Nepean Sandstone (overlooking the older portions of the Potsdam), renamed Logan’s passage beds as the March Formation, and renamed the Calciferous as the Oxford Formation.

Wilson (1937 & 1938),  described the March Formation unit as being composed of "thick beds of interstratified grey sandstones with a calcareous cement and sandy blue-grey dolomites, both weathering a rusty brown".   Her 1946 description was “The March formation consists of alternating grey sandstone and sandy dolomite or blue-grey dolomite, all weathering dark rusty brown. ... The formation represents a transition from the Nepean sandstone to the Oxford Dolomite, the sand content being most evident at the base..”  She stated that “The lower contact [with the Nepean sandstone] is placed arbitrarily at the lowest dolomitic layer.”



In the quarry where I was collecting things are more complicated.  Anything goes.   While the predominant rock is sandstone, I’ve found dolostone, mudstone, siltstone, minor shale, and a bit of limestone.  The sandstones, mudstones and siltstones can be just about any colour (reddish, brown, ochre, black, grey, tan, etc.).   There are many examples of mud cracks and ripple marks, and possible microbial mat structures.   

[2019:  I have retracted a number of paragraphs from the original post.  I did this because I failed to recognize that I had found Ediacaran fossils.    The discs shown under number 7 below are Aspidella.  Under number 4, the sixth and seventh photos show Ediacaran fronds.   Most of the photos show  Ediacaran fossils or microbial mat textures.  See my March, 2019 postings for a better explanation.
At most only the top layers of the quarry are March Formation.  ]

The Fossils

Below I’ve provided the photographs.  I had hoped to go through and look up the scientific names for the fossils.  As that hasn’t happened over the past year,  I’ve decided to put a selection of photographs on my blog to stimulate interest in the Drummond Sequence..   I’ve grouped the fossils in a way that makes sense to me.

1.  Bedding Parallel Burrows in a bed close to the top of this section of the quarry.
Sam_0180 and 182
 





2.  Simple cylindrical, curving burrows roughly parallel to bedding plane
Sam_0037




3.  Larger, rougher, cylindrical, curving burrows  roughly parallel to bedding plane
Sam_0525


4   Branching, overlapping, possibly interpenetrating, roughly parallel to bedding plane
P820760, Sam_0016,  Sam_0023,  Sam_00 31, Sam_00 34, Sam_0102, Sam_0140






5    Faint Circles: Medusae or discoid holdfast?
P820758






6   Discs and concentric cylindrical features parallel to bedding plane: discoid holdfasts.
Sam_00 40,    Sam_0138, Sam_0149














7   A Congestion/Colony of Multiple discoid holdfasts
Sam_0121 & 123 - same slab


 8    Lindt Truffles (circular, about the size of the candy, with a thin 2-4 mm rim and a different coloured centre)  - 
Sam_0046 & 47    




9    Thin Film, barely there
Sam_0053



10   Sam_0070, 71, 73, 75




11   Stromatolite  (Dr. Al Donaldson's identification)
Sam_0129





I hope these photographs stimulate interest in these rocks.

Christopher Brett
Perth, Ontario

Thursday, 29 August 2013

Abraham, Logan and Owen: The Discovery of the First Protichnites trackways – Part 1


“Protichnites is from the Greek Protos, the first, – Ichnos, foot-print, or track, – and Lithos, stone; literally – The first stone foot-prints.”  (Elkanah Billings, 1857) 

“PROTICHNITES (Gr. protos, first; ichnos, footprint)” (H. Alleyne Nicholson, 1876)

I suspect that everyone who has looked at the trackway that is the trace fossil Protichnites is aware that the first specimens were found in a quarry on the west side of the St. Louis River at Beauharnois, Quebec, that the first reports in the scientific papers were papers read before the Geological Society of London on April 30, 1851 by W. E. Logan and Professor Owen, that in the field season of 1851 W. E. Logan returned to Canada and with the aid of Mr. Richardson found numerous examples of similar trackways, principally at Henault’s field (a half mile west of the quarry on the River St. Louis),  that in 1852 W. E. Logan and Professor Owen again presented papers before the Geological Society of London, that numerous drawings of the trackways accompanied the two papers,  and that in Professor Owen’s paper the trackways were given the name Protichnites.  

In his papers and reports Logan named the others besides himself  who deserved credit for finding the initial trackways, and while Logan named the most significant contributors, their contributions are often overlooked.  These named individuals are:

 - Mr. Abraham, Editor of the Montreal Gazette,
 - Mr. James Richardson, an employee of the Geological Survey of Canada, and
 - Mr. Alexander Murray, Assistant Provincial Geologist at the Geological Survey of Canada.

Various unnamed quarrymen were also singled out by Logan.

Below I’ve also mentioned two other individuals:  Sir Charles Lyell (a British lawyer and the foremost geologist of his day, who in his era  published the most widely read books on geology) and Sir Roderick Impey Murchison (the author of comprehensive work on the Silurian System in Great Britain and elsewhere).   Lyell promoted Logan’s discovery  while Murchison initially questioned its importance.  In part this is because Logan’s discovery called into question part of the latter’s book, Siluria, which described the geology and fossil content of much of the  Paleozoic.

Today we accept that the trackmakers that left the Protichnites  trackways were likely the first creatures to leave the oceans and walk on land.   It is interesting to step back in time and take a brief look at the disbelief, the furor and amazement that the discovery of Protichnites trackways created, and at the speed with which the discovery circulated among geologists in England, Canada and the United States.

Below I’ve provided the important dates.  When looking at the dates it is important to keep in mind that before Logan and Owen presented their papers in 1851 and 1852  the accepted belief was that before the Devonian  no creature walked on land.   It is also worth noting that what we now call the Cambrian and Ordovician were encompassed at that time within the Lower Silurian.  It was an important time in the development of geology, and ideas were changing rapidly.   In 1852  Lyell and Dawson made the celebrated discovery of tetrapod fossils entombed within an upright fossil tree at Joggins, Nova Scotia.     It was not until 1859 that Darwin published On the Origin of Species and it was not until 1879 that the Ordovician was defined.   It had not  been two decades since Charles Lyell's multi-volume Principles of Geology was published from 1830 to 1833 .   Wikipedia comments that Lyell “developed Hutton's idea that the earth was shaped entirely by slow-moving forces still in operation today, acting over a very long period of time. The terms uniformitarianism for this idea, and catastrophism for the opposing viewpoint, were coined by William Whewell in a review of Lyell's book.  Principles of Geology was the most influential geological work in the middle of the 19th century.”

To understand what is written below one also  has to have at least  a passing understanding of the references to the “Old red sandstone.”   This is a  British a sequence of rock strata  which is of considerable importance to early paleontology.  In Logan’s time they were known as a sequence of Devonian rocks  that are continental rather than marine in origin.  The fossil fauna is characterized by primitive fishes.  Near the top of the  succession were found the first terrestrial tetrapod vertebrates.  Today these rocks are mapped as extending from the late Silurian into the Devonian and on into the earliest part of the Carboniferous.  Many early papers reference the Old Red Sandstone.

The Important Dates Concerning  the Discovery of Protichnites

These are the important dates:

1847 - Mr.  Robert Abraham, Editor of the Montreal Gazette, reports in his newspaper the discovery of the track in a sandstone quarry at Beauharnois, Quebec

1847 - Mr. Abraham brings the  tracks  to the attention of W. E. Logan.  They are delayed by circumstances one year, and a premature and early snow the next, from visiting the occurrence.

1849 or 50 - W. E. Logan and Robert Abraham visit the site .  (Later Mr. Sterry Hunt, Chemist to the Geological Survey of Canada, visits the site and finds many more tracks.)

December, 1850 - W. E. Logan has two specimens quarried from the quarry on the west side of the St. Louis River at Beauharnois, Quebec and has casts made of the larger specimen

Winter of 1851 – After the boats have left the St. Lawrence, Logan sails for London from Boston, taking with him a small slab bearing the trackway and six plaster casts of the large specimen, which weighs over a ton and is 12 and half feet in length. The original slab, because of its size, is left  in the museum at Montreal connected with the Geological Survey of Canada.

March 18, 1851- Professor Owen sends a letter to Sir Charles Lyell, President to the Geological Society of London, commenting on the tracks (which is published as an addendum to Lyell’s February 18th Anniversary Address of the President to the Geological Society of London).  The letter is a condensed version of the paper he presents in April.

April 30, 1851 -  W. E. Logan and Professor Owen read papers before the Geological Society of London, exhibiting the small specimen and the casts.    Important geologists, including Sir Roderick I. Murchison, contest the conclusions in the paper, doubting that the rock is as old as proposed by Logan.

July, 1851 - W. E. Logan exhibits the small specimen and the casts at a Meeting of the British Association for the Advancement of Science held at Ipswich, England.  Logan’s talk is well received.

July, 1851 - The addendum to Lyell’s February 18th Anniversary Address of the President, including  Professor Owen’s letter to Sir Charles Lyell, is published in The American Journal of Science and Arts

Field Season 1851 - Forty-three  trackways are found in four areas in  Henault’s field (a half mile west of the quarry on the River St. Louis).  Additional  trackways are found two and a half miles further westward close to the mouth of the Beauharnois Canal, on one of the Islands of St. GĂ©neviève, in the vicinity of Point Cavagnol (on the south side of Lake of Two Mountains in Vaudreuil), in the vicinity of Pointe du Grand DĂ©troit in Vaudreuil, at the summit of the escarpment along the Rivière du Nord at Lachute,  and in Lansdowne and Bastard counties in Ontario.

September, 1851 - Robert Abraham publishes an article describing finding the occurrence, bringing it to Mr. Logan’s attention, his visit to the site with Logan

January 6, 1852 -  Logan again sails for London, taking with him the original 12 ½ foot slab, a second slab from Henault’s field measuring 8 feet,  a third slab with two tracks and ripple marks upon it from one of the Islands of St. GĂ©neviève, and one hundred casts of trackways  from Henault’s field.

February 21, 1852 - Logan writes to his brother James that “I am engaged night after night with Owen in the examination of the tracks, which make a wonderful display on the floor of the Geological Society. They cover the whole centre of the room. .. The anniversary of the Society took place yesterday, and the tracks excited great interest.”

After February 20, 1852- Owen sends a communication  to William Hopkins, the new President of the Geological Society of London, advising that the tracks belong to Crustaceans.  This is published as an addendum to the Anniversary Address of the President that was delivered on February 20th

1852 - Before March 24 - The fourth edition of Sir Charles Lyell’s  text A Manual of Elementary Geology is published.  Lyell devotes over two pages to the tracks, noting that “numerous other trails have since been observed ...and Mr. Logan, who has visited those places, will shortly publish a description of the phenomena.”

March 24, 1852 - W. E. Logan and Professor Owen read papers before the Geological Society of London.  Following the papers, Logan reports “there was a glorious discussion.”  Logan temporarily deposits the 8 foot slab from Henault’s field (bearing Protichnites latus) with the Society’s Museum, and deposits casts from Henault’s field (including the tracks Protichnites 7-notatus, Protichnites lineatus and Protichnites alternans) in the British Museum

Robert Abraham’s Discovery

The discovery of the first trackway that was later identified as Protichnites is reported concisely in a paper by Elkanah Billings published in 1857, who mentions:

    “In 1847, the late Mr. Abraham, then Editor of the Montreal Gazette, announced in his paper that the tracks of a tortoise had been discovered in the sandstone of Beauharnois.  He supposed this rock to be the equivalent of the old red sandstone, and, as previous to the publication of his notice no remains of reptiles had been found in formations of so ancient a date, these were regarded by him as particularly interesting.  Mr. Logan’s attention was afterwards drawn to the discovery...”

Logan acknowledged Mr. Abraham’s contribution stating  (a) in his 1851 paper that “My attention was first drawn to the track by Mr. Abraham, then editor of the Montreal Gazette, who duly appreciated its possible geological importance, and inserted a notice of it in his daily journal.”, (b) in the Report of Progress for the Year 1851-52 “The occurrence of the track near the mill by the St. Louis River at Beauharnois, had been pointed out to me by Mr. Arbraham, then editor of the Montreal Gazette, who had introduced a notice of it in his Journal, in which he compared it to the track of a tortoise.” and (c) in his 1863 book the Geology of Canada “The first track discovered was met with near the mill on the St. Louis River at Beauharnois; and the late Mr. Abraham, editor of the Montreal Gazette, was the first to draw attention to it, by notice in his journal, in which he compared it to a tortoise.”

Mr. Abraham’s contribution was acknowledged by Sir Charles Lyell, who commented in the addendum to his Anniversary Address  mentioned above, that  “The markings were first pointed out to Mr. Logan by Mr. Abraham, editor of the Montreal Gazette, who appreciated their geological significance.”

Sir Charles Lyell gave Robert Abraham even more credit in 1852 when he published the fourth edition of  his text A Manual of Elementary Geology, where  two full pages,  and a part of a third,  are devoted to the tracks.  Lyell starts off his report with the sentences “In the year 1847, Mr. Robert Abraham announced in the Montreal Gazette, of which he was the editor, that the track of a freshwater tortoise had been observed on the surface of stratum of sandstone in a quarry opened on the banks of the St. Lawrence at Beauharnois in Upper Canada.... Imagining the rock to be the lowest member of the old red sandstone, he was aware that no traces had as yet been found of a reptile in strata of such antiquity.   He was soon informed by Mr. Logan ... that the white sandstone above Montreal was really much older than the “Old Red, ” or Devonian.  It had in fact been ascertained ... to lie at the base of the whole Silurian series.”   Later  Lyell  notes that Mr. Abraham “was aware that no traces had as yet been found of a reptile in strata of such high antiquity” and that “Mr. Abraham has inferred that breadth of the quadruped was from five to seven inches.”

I have not been able to find the original article from the 1847 Montreal Gazette.  I did find an article by Robert  Abraham that was submitted on August 25, 1851 and published in September, 1851  where he describes finding the track, publishing his announcement in the Montreal Gazette, bringing it to the attention of W.E. Logan, and visiting the site with Logan.   Here is a condensed  version, in Robert  Abraham's own words:

    “About four years ago, when on the road to Beauharnois, I met Mr. Macmaster, of the Seigniory Mill of that village, who... told me that in the quarries above him, there were the tracks visible of a common mud-turtle or terrapin...  I told him it was impossible, that no animal existed or could exist, at the time those rocks were deposited.    He persisted... We accordingly went up to the quarry, when I wondered,  and was convinced.   Doubt there could be none that this was the path of a quadruped of some sort or other...

    Mr. Logan was at that time from home, I think surveying the basins on the New Brunswick frontier.  I published an account of the discovery in the Montreal Gazette... At that time I as under the impression ... that the rock was the oldest member of the old red sandstone series... Bold and brash that I was, I did not hesitate to express my opinion that the track really was that of a tortoise.

    When Mr. Logan returned, towards the close of the autumn, he saw my paper, and though he had no doubt that the traces were those of an undescribed animal, he could not believe that they were those of a Chelonian reptile...  And, moreover, he told me that the rock was even older than I had supposed;... belonging...to the lower Silurian series.   The track might, he thought, be a of a gigantic centipede or millipede... I made a rude drawing... To this he objected, that an idle boy might have made a series of marks with a pickaxe, to produce the effect delineated.    I answered ... that no human skill could produce the median trail with raised edges, whether due to a tail or to the convexity of a breastplate dragging through mud; that there were twelve or fifteen feet of a stratum of rock, about fifteen inches thick, under which the trail entered, and the other came out...

    [Mr. Logan] arranged with me to go and look at the rock.  Circumstances prevented him from doing so that year.  The next year we were interrupted by a premature and heavy snow.  On the third year he went with me, and wondered, as I had wondered before.  The portions exposed had suffered from much from the action of frost and sun, but there was quite enough unexposed, to be quarried out, fresh and perfect.  Mr. Logan took the opportunity of the great Exhibition, to lay casts and specimens before the Geological Society of London.    ... [He] placed my original article in the hands of the Society, and Sir Charles Lyell has distinctly stated the material point, that I was aware of the importance of the discovery.

    ...  I saw three impressions, including the one preserved;  but Mr. Hunt, Chemist to the Geological establishment, has since been to the spot, and has found many more, including one striking phenomenon,  where the foot of the creature has struck against a wave-marked ripple on what was then the sand.  Mr. Logan has just informed me that many more have been detected.”

An interesting description by a person that Logan and others describe merely as the editor of the Montreal Gazette.   It begs the question:  Who was Robert Abraham?  Various sources provide the answer:  he was a man for all seasons.  He was an Englishman from Cumberland.    He trained as a medical doctor, graduating from the University of Edinburgh, but soon was drawn  to journalism.   He was medical editor of the Liverpool Journal before he emigrated to Canada and bought the Montreal Gazette in 1843 or 1844.  He was the editor of the Gazette until 1848, and is supposed to have been an able writer but a militant journalist.  After he sold the Montreal Gazette he became a lawyer, and was admitted to practice as an advocate in Lower Canada.  He then returned as an editor of a newspaper and of an agricultural journal.   He died at Montreal on November 10,  1854.

Above all, Robert Abraham was a writer.   An example of his legal writing is the booklet published in 1849 entitled Some remarks upon the French tenure of "franc aleu roturier", and on its relation to the feudal and other tenures (that is available from archive.org).   An example of Robert Abraham's writing on natural history is his 1851 article entitled Tracks of a Chelonian Reptile in the Lower Silurian formation, at Beauharnois , The British American Medical & Physical Journal, Volume 7, pages 195-200 (an article that I suspect had probably not seen the light of day for well over a century until I happened upon it).  An example of his medical writing is Case of Sanguineous Apolexy, 1825, The Edinburgh Medical and Surgical Journal, volume 24, pages 301-304

Medical doctor, editor, militant journalist, lawyer,  writer and the first to realize the significance of the tracks at Beauharnois.  Quite a career.

A few additional details of his life can be found in a paper presented in 1869 by Sir Robert Gibb entitled Discoveries in Science by the Medical Philosopher, An Oration delivered to the Medical Society of London, which discusses the contributions of numerous medical doctors.   Sir Robert Gibb mentions that Robert Abraham, an Englishman,  “whom I had the pleasure of knowing well”, “was a surgeon, a Member of the London College, who at one time was in practice in Carlisle, and emigrated to Canada, where he became the Editor of the Montreal Gazette, a daily newspaper.”  Those are the only facts about Mr. Abraham that Gibb can provide, though he speculates  “Although we have no information concerning the student life of and early history of Robert Abraham, ... it is but fair to infer that the study of the animal world was not neglected by him before he became a member of the profession of which we all feel proud.” 

In the notice of Robert Abraham's passing the Gazette highlighted his editorial writing, but also mentioned:

“ As a geologist and naturalist (particularly in his favourite branch of Natural History, Entomology) he had few equals in Canada– perhaps no superior on this continent.”

[I have not been able to find any of Robert Abraham’s writings on Entomology, but note that Canadians would have been more likely to have chosen W. E. Logan as the preeminent geologist on the continent, while Americans might have chosen Ebenezeer Emmons, James Hall or James Dwight Dana.]

Interestingly, Sir William Gibb, M.D.,  visited Abraham’s discovery in August, 1851.   He states:

    “Possessing myself some knowledge of the Science of Geology, ... I was forcibly struck with Abraham’s discovery, and when I first visited the locality where these impressions existed in August 1851 – eighteen years ago, before many of them had been disturbed,....”

Wouldn’t we all have liked to have visited the Beauharnois area in 1851.

Sadly,  after about 1910  Mr. Abraham’s name is rarely mentioned in conjunction with the discovery of the trackways at Beauharnois.  The discovery is often credited to Logan and Owen.

++++++++++++++++++++++++++++++++++++++++++

Part 2 on Protichnites will cover Logan’s two visits to England in 1851 and 1852

Christopher P. Brett
Perth, Ontario

Tuesday, 27 August 2013

Odd. Even for the Potsdam


Below are a number of photographs of slabs of sandstone from Burgess Ward, Tay Valley Township, Lanark County, Ontario.   The area has been consistently mapped as Potsdam Group sandstone, which is from Middle to Upper Cambrian in age. 

The sandstone at this location exhibits two facies: a wind blown facies evidenced by very fine cross bedding, and an aquatic facies evidenced by burrows (including  U-shaped burrows that are Diplocraterion, and single burrows perpendicular to the bedding plane).  The outcrop at this location is a drainage ditch, close to which are a number of piles of sandstone.   Every time I visit I find something interesting. 

First Slab: Photographs Sam_0499, 0500, 0501

These photos are likely of the sole of the slab, as it appears from photo 501 that the sand filled in a depression.  Whether the depression was caused by burrowing or a vortex (caused by wind or water) is not clear.  It is unfortunate that half of the depression is missing as one needs the missing half to tell whether the depression is a spiral.


Second Slab
Both the top and bottom of this slab are interesting.  The top can be determined because of the V-shaped burrowing on one side.

Thin Brown Lines on Top of Second Slab: Photographs Sam_0471 and 0472

While these could easily be recent staining along roots, or staining cause by water seeping along fine cracks, I’ll have to pass this by an ichnologist and paleontologist  before I rule it out as being a fossil.  It would be particularly interesting if it were an algae from the Middle to Upper Cambrian.



[Added September 15, 2022:]   Another possibility is that this is a fossil graptolite.  See the graptolites in Figure 3 in the following paper:
Geyer, G., Landing, E., Meier, S. et al. , 2022, Oldest known West Gondwanan graptolite: Ovetograptus? sp. (lower Agdzian/lowest Wuliuan; basal Middle Cambrian) of the Franconian Forest, Germany, and review of pre-Furongian graptolithoids. PalZ (2022). 
https://doi.org/10.1007/s12542-022-00627-5



Sole of Second Slab
White polygonal  pattern within troughs in ripple marks: Photographs Sam_0507 and 0487



 




A number of the polygons are hexagons, but many are not.   The sides of the polygons are about 5 mm in length and about 2 mm thick.    Normally one would think that a polygonal pattern found on the bedding plane of a sedimentary rock is made by the infilling of desiccation cracks.   However, there are two reasons why the polygonal shapes in the photos  may not be desiccation cracks.  First,  this rock is sandstone and sand on drying doesn’t contract by the amount required to form the polygons shown in the photos.   Second, the sides of the polygons are  ellipsoidal to  cylindrical in cross-section and resemble burrows.

Is this  a trace fossil somewhat like Paleodictyon?  Possibly.  Paleodictyon consists of a network of hexagonal meshes and has been found in rocks ranging in age from the Cambrian to recent times.   Photographs of Paleodictyon can be found on Wikipedia  and by simply searching the word in Google images   (See, for example:  http://en.wikipedia.org/wiki/Paleodictyon
 http://hexnet.org/content/paleodictyon  )   The polygonal pattern on the slab that I have found resembles a number of the examples of trace fossils that others have identified as Paleodictyon.
   
Another possibility for the polygonal  patterns is that they are evidence of microbial mat shrinkage cracks.

Crystals on Sole of Second Slab: Photo Sam_0506 (and above two photos)

These crystals are interesting.   They are not calcite, as they don’t effervesce in dilute acid.  From the colour and luster they appear to be gypsum, but the crystal system appears to be wrong for gypsum.   I might have to beg a favour and pass a sample to a friend with access to a scanning electron microprobe.







Third Slab: Microbial Mat Shrinkage Cracks

The next photo, Sam_0510, shows three crescent shapes in the troughs of ripple marks in sandstone.   I believe these curved shapes  to be evidence of microbial mat shrinkage cracks (see my blog posting from November 5, 2012).




Fourth Slab: Burrowing in Ripple Marks: Sam_0475

I believe this to be burrowing as the hand specimen shows one sandstone tube going under the other.  (I admit that the photo could be clearer.)









Fifth Slab: Diplocraterion: Sam_0464

I’m including this photo, not because the trace fossil is odd (it’s fairly common), but because I found a sample that shows a good cross-section of three Diplocraterion traces.  (The top of the slab is on the right hand side of the photo.)







Christopher Brett
Perth, Ontario

Monday, 12 August 2013

The Trace Fossil Diplichnites – A New Occurrence in Eastern Ontario

 The trace fossil Diplichnites was named by Professor Dawson of McGill University in a paper presented about 140 years ago.   It is a trackway that consists of two parallel rows of blunt to elongate to ellipsoidal, closely spaced tracks.   It can be contrasted with the trace fossil Protichnites which is a trackway that consists of two parallel rows of imprints surrounding a medial impression.

Interestingly, the trace fossil Protichnites and the trace fossil Diplichnites are often found at the same occurrence.    For example, Alexander Murray of the Geological Survey of Canada reported on such an occurrence in 1852, the same year  William E. Logan and Professor Owen were presenting the initial papers on Protichnites.  

Various researchers have commented on the association of Protichnites with Diplichnites.  A few have suggested that “the Diplichnites may have been undertracks that penetrated to the underlying layer of sediment, and the fossil trackways thus produced on the top surface (preserving the impression of the dragging tail) were Protichnites” (Wikipedia).     In contrast, others suggest that the Diplichnites tracks occur on the surface.  For example, a recent paper discussing a few Diplichnites trackways in the Potsdam Group sandstones in Quebec mentions that  “Examples with pushback mounds and examples that occur on bed surfaces with adhesion structures are not likely undertracks; their lack of central drag marks suggest that some tracemakers held their tails aloft...” (Hagadorn, Lacelle and Groulx, 2012).   A third possibility is that the tracksways grade into one another.    This was noted by a researcher who reported that  “Several tracks of  Diplichnites are also present, with a medial drag mark appearing in places, grading into  Protichnites.” (Charles. T. Hoxie, 2005).

Below I’ve provided photographs of specimens of Diplichnites trackways from the same outlier of Potsdam Group sandstone between Kingston and Perth where I found the specimens of Protichnites mentioned in my last blog posting.

Photos SAM_0491  and SAM_0492 were taken of the same slab.  They show a Diplichnites trackway (two parallel rows of  tracks) crossing ripple marks.   This is likely the sole of an overturned slab, as the footprints are in positive relief.



Photo SAM_0435.JPG is a different slab.    It clearly shows two parallel rows of tracks.






Photo SAM_0438.JPG  is a  specimen  that  was collected close to the specimen shown in Photo SAM_0435.JPG.  There is one good  line of circles (arguably paired  with another line of circles),  plus     crossing lines of  circles,  plus numerous  other circles.




  

Below are photos   SAM_0495 and SAM_0497 of two slabs that might bear the trackway Diplichnites.






       

Christopher P. Brett
Perth, Ontario